What was found
ON AFTER START CHECKLIST GOT ZONE TEMP ON CONT CAB WENT AWAY AFTER MASTER CAUTION RESET. GROUNDED - YES. PERFORMED BITE OF PACK/ZONE TEMP CONTROLLER PER B737-800 FIM 21-62-TASK 801, FOUND FLIGHT DECK TRIM VALVE FAULT, UPON VERIFY TEST FAULT WAS RESET FIM 21-62 TASK 832, CLEANED CONTROL CABIN SENSOR AND FILTER, PERFORMED CABIN TEMP CONTROL AND INDICATION OPERATIONAL TEST PER B737-800 AMM 21-61-00-700-807-002.